model ClassicGravitation
  parameter Real    G=6.674e-11             "Gravitational Constant";
  Real              m1(unit="kilogram")     "mass #1";
  Real              m2(unit="kilogram")     "mass #2";
  Real              r(unit="meter")         "radius";
  Real              F                       "force";
equation
  F = (G * m1 * m2) / (r^2);
end ClassicGravitation;